January 5, 2014

US Seasonal Flu Widespread With H1N1 As The Dominant Strain

The 2013-2014 influenza season is underway in the United States, with more than half the country reporting widespread cases of flu activity, according to the US Centers for Disease Control and Prevention (CDC).

While last year’s flu season was one of the worst in recent years in the US, one of this year’s strains – H1N1 – is making up more than half of the cases so far reported. It was during the 2009-2010 flu season that H1N1 caused a global pandemic, spreading from central Mexico to more than 70 other countries, killing in the neighborhood of 284,000 people, according to the CDC.

In just the past week, the number of states reporting above average cases of seasonal flu jumped from 10 to 25, with widespread activity reported in Alabama, Alaska, Arkansas, Colorado, Connecticut, Georgia, Idaho, Illinois, Indiana, Kansas, Louisiana, Massachusetts, Minnesota, Nebraska, Nevada, New York, North Carolina, Oklahoma, Oregon, Pennsylvania, Texas, Utah, Virginia, Washington state and Wyoming.

According to the CDC, "widespread activity" means that more than 50 percent of geographic regions within a state are reporting flu activity. This particular CDC data measures the overall spread of flu, but not the severity of illnesses.

The flu is responsible for thousands of deaths each year in the US, with peak activity from October to March. This season, the flu is spreading relatively quickly.

"We are seeing a big uptick in disease in the past couple of weeks. The virus is all around the United States right now," Dr. Joe Bresee, chief of Epidemiology and Prevention in the CDC's Influenza Division, told Reuters.

During the 2009-2010 flu season, younger people were more susceptible to H1N1. This year it is still too early to tell if the same age group will be most at risk, noted Bresee.

At least six children have died as a result of influenza this year, according to CDC data.

"There is still a lot of season to come. If folks haven't been vaccinated, we recommend they do it now," Bresee said.

He said that flu cases usually peak in January and February, noting that the only difference this year is that H1N1 is the most common strain.

H1N1, which was called swine flu when it broke out around the world in 2009, has maintained a human presence in each flu season since then. Because of this, H1N1 is no longer regarded as swine flu but rather a human seasonal virus, according to Jhung.

In fact, the H1N1 strain is now so common, it was included in this year’s vaccine.

While it is difficult to track illnesses and deaths of each particular strain, CDC data estimates that 381,000 US citizens were hospitalized last year due to influenza; 171 children had also died during the 2012-2013 flu season, which health experts have called a relatively severe season.

Still, flu vaccinations last year prevented 6.6 million illnesses, 3.2 million doctor visits and at least 79,000 hospitalizations, the CDC reported.

Flu vaccines are recommended for all people over the age of six months, especially those who are pregnant and at high risk of complications, which includes the elderly, children under the age of five and those with underlying medical conditions or who have compromised immunity.

For those who do get sick, antiviral medications are a good treatment, Jhung told CNN. He added that antivirals should be administered within two days of the first sign of symptoms for the best effect.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota in Minneapolis, told USA Today’s Elizabeth Weise that this year is looking a lot different than last year’s flu season.

H3N2 was the dominant strain in 2012-2013 and was responsible for a larger number of deaths in older people. With H1N1 being the main strain this year, “we fully expect to see many more cases in younger children and middle-aged adults," Osterholm told Weise.

"Mark my word, by the end of next week we'll probably see some fear and panic as it starts to hit kids," Osterholm added.

On a positive note, H1N1 has not had much time to develop a resistance to antiviral drugs such as Tamiflu, noted Bresee.

In Texas, where 25 people have so far died from this season’s flu outbreak, the Texas Department of State Health Services issued an “influenza health alert,” advising clinicians to consider antiviral treatment when necessary, even if an initial rapid-flu test comes back negative. It is also urging all citizens to get the annual flu shot.

"The flu is considered widespread in Texas," Carrie Williams, a spokeswoman for the state's health department, said in a statement to Reuters.